The present invention relates to the field of bridge construction, and more particularly, the construction of precast segmental bridges, especially those having multiple bridge spans, wherein successive bridge segments are positioned and attached to existing bridge components.
Precast segmental bridges are known and commonly used throughout the world as a means to forge roadways through mountainous terrain or across rivers and other natural barriers. Such bridges are typically constructed in accordance with the following sequence: First, a series of upright piers are formed along the bridge span. Thereafter, cantilevered bridge sections are built out from each pier by successively mounting the precast segments to previously completed bridge components and post-tensioning the segments thereto. The cantilevered bridge sections are built out from each pier in a symmetrical fashion so that the piers are not subjected to undue bending loads. When the cantilever sections are complete, the ends thereof are post-tensioned together to form a continuous bridge deck. Typically, two such bridge spans are constructed to accommodate the two directions of travel. These spans run generally side-by-side, but need not be parallel (horizontally or vertically) nor at the same elevation.
Prior techniques employed in the construction of precast segmental bridges have relied on use of a single piece of equipment able to erect one deck at a time, starting from one end and finishing at the other end of the bridge. In the case where several decks were erected, the piece of equipment had to be repeatedly used, or two or more pieces of equipment were used simultaneously. Both options added significant time and expense to bridge construction.
The most frequently used techniques in the past involve the use of a launching girder resting on top of the deck under construction. Such techniques have been used, for example, at Rio-Niteroi Bridge, Brazil where four (4) launching girders (two at each end of the bridge) were used simultaneously to build two (2) parallel decks at the same elevation. Similarly, at Chillon Viaducts, Switzerland, a single launching girder was used to build two parallel decks, at different elevations, with each deck being built independently, one after the other.